Rotel 1095 humming

[Rags]

Hi everyone - Im new to Rotel - I just picked up a RMB1095 yesterday. Sounds wonderful running off the processor in my Yamaha DSPA2 (temporarily).

However I can hear a slight humming sound when the amp is switched on - intitally I though it might be the fan in the amp but then I recalled that it does not have a fan. The humming was particularily audible late last night when everything else was pretty quiet. So far the ony connections I have made are the Yamaha's preouts to the amp, the amp to the speakers and an optical input into the yamaha from a dvd player. The Rotel is not faulty as I have heard this very amp in another setup with no audible hum

I know this thing is a beast and draws a lot of current but is this normal ? I am running 4 ohm speakers.

Any advice / help would be appreciated. Maybe im just being picky....

Thanks
Rags

[Andrew Pratt]

Rags you've very likely got a grounding problem somewhere in your system that the amp is picking up. The most common culprit is the coax cable feed from the cable or satellite dish not bing properly grounded. As a test unplug all coax cables from your VCR's, TIVO's and satellite receivers etc and see if the humming goes away. If it does you'll need a grounding block installed on these coax cables which you can find at most radio shacks for a couple of dollars. Keep us posted and we'll get you sorted out.

[Rags]

Andrew - my satellite, VCR etc although on the same rack have not been connected up to the amp/processor (yet). Why would this still cause a problem ?

Thanks
Rags

[greggz]

Rags, please clarify, is the humming coming from the speakers or is it actually eminating out of the amp itself?




Gregg

[Rags]

Gregg / Andrew - it's coming mostly from the rear speakers. But it is faint - only notice it in silent moments. I have four power sockets next to each other and one of them is being used by the amp. If I switch on the amp with the other sockets off I there is no hum. However if I switch on the socket which has the DVD player, sat receiver and TV connected to it and then switch on the amp the humming starts. The other two sockets which are used by the subwoofer and the processor have no effect on the power amp whatsoever (ie no humming is heard regardless of whether they are on or off).

Thanks
Rags

[Andrew Pratt]

Since the sat receiver's on that socket that's causing the problem try unplugging the coax cable from it and then plug things back in...I still think its likely a weak ground on the coax cable from the dish.

[Rags]

Actually I have two sat receivers connected to that socket. I will disconnect the coax ccables (as soon as I can get the wife to stop watching the box) - will report back shortly.

Thanks for your support.

[Rags]

Andrew - Ok disconnected the coax cables and no effect - humming still there. However the problem is related so thanks for the input - the outputs from the sats feed into a small RF amplifier sitting at the back of my av rack - this then sends the signal to all parts of the house - when I switch this rf amp off the humming goes away. Problem is if I switch off the amp then no one can watch tv in the rest of the house (not such a bad thing on reflection). Is there any way to get rid of the problem ?

Thanks
Rags

[Andrew Pratt]

Ah so now we're getting somewhere. I assume the RF amp is powered right? If so where is it plugged into? Try plugging that into the same socket as the amp and see what happens. Failing that one of the coax grounding blocks attached to the amp and grouned to the water pipe might fix the problem.

[Rags]

Yup it's powered. Tried to connect both to the same socket but humming continues. Will try to rewire the whole damn setup tomorrow.

What would happen if I removed the earth wire from the rf amps power plug ?

[Andrew Pratt]

Rags that might work but you'll now have a floating ground which could be a potential electrical hazzard. There's a reason "cheater" plugs are illegal in Canada That said it wouldn't hurt to make a cheater plug or buy one and see if that helps...if it does buy a grounding plug from radio shack and install that...they're only $3 and a couple of dollars for a copper grounding wire so its not a ton of money and will be much safer then removing the ground